This invention relates to a prosthesis implantation inserter for use with a flexible acetabular cup. Flexible acetabular cups have shown their ability to transfer the load in a natural manner to the patient's pelvis. An acetabular cup of this kind is described in U.S. Pat. No. 5,609,646 the disclosure of which is incorporated herein by reference.
To achieve an initial stability and a long term implantation of a flexible acetabular cup prosthesis it is necessary to ensure that the position of the implant is appropriate and that the contact between the bone and the outer surface of the prosthesis is maximized. Moreover, the stability is achieved due to an interference fit between the host bone cavity and the implant. The outcome during the implantation is its inclination to deform itself. As a consequence, it is difficult to place the acetabular cup adequately and guarantee an intimate contact with the bone. The present invention is intended to provide an instrument to overcome these difficulties.
U.S. Pat. No. 5,954,727 shows a positioning tool for reversibly engaging an acetabular cup, an elongate cylindrical section of the positioning tool being insertable through a posterior opening in the cup. The outer diameter of the cylindrical portion is expandable to engage the inner wall of the cup in an interference fit to prevent movement of the cup relative to the tool and hold the cup in engagement when planting the cup at a desired position.
U.S. Pat. No. 5,098,437 also shows the use of a positioning rod which has spring elements which engage a circumferential groove on the inner surface of the implant.
Neither of these constructions are suitable for use with a flexible acetabular cup due to the flexibility of the cup itself.
In U.S Pat. No. 5,609,646 the flexibility of the cup is provided by the materials from which it is fabricated and a separation or opening in its peripheral rim and the present invention utilizes one opening or separation of this type.